Study On Chemical Extraction Of Lithium From Leaching Residue Of Lithium Mica

With the proposal of the dual-carbon strategy,the market demand for lithium is huge.Like other metal smelting and purification,a large amount of lithium leaching slag will be produced in the process of lithium extraction and stored around the plant area（taking Yichun,Jiangxi as an example,the production of 1 ton of lithium carbonate will produce 20-30 tons of lithium leaching slag）.With the continuous development of lithium resources,the storage of lithium leaching residue will seriously affect the normal production of enterprises and threaten the surrounding ecological environment.Lithium leaching slag contains rich Si O₂ and Al₂O₃.Scholars have tried to use lithium leaching slag to prepare cement,concrete,unburned brick and other building materials.However,due to the high content of potassium,sodium,sulfur and other elements in lithium leaching slag,it is difficult to realize large-scale utilization of lithium leaching slag as building materials.At the same time,the lithium leaching residue also contains some valuable metals such as lithium,rubidium and cesium,which has high recycling value.However,there are few studies on the recovery of valuable metals from lithium leaching residues at present.Therefore,this article has explored the process research of direct acid leaching and"roasting ultrasonic enhanced leaching"for extracting lithium from the leached residue of lithium mica in Yichun,Jiangxi Province.The main research results are as follows:（1）The optimal parameters for the direct acid leaching process of lithium are:sulfuric acid as the leaching agent,concentration of 1mol·L^-1,leaching temperature of50℃,leaching time of 120 min,liquid-solid ratio of 10:1,and lithium leaching rate of66.56%.The content of Li,K,Na,and S in the secondary leaching residue is 0.17%,1.45%,1.23%,and 8.12%,respectively.（2）The optimal parameters for the roasting leaching process are:the roasting additive is a mixture of ammonium chloride and calcium chloride,with a mass ratio of1:1,the mass ratio of lithium slag to additive is 1:1.25,the roasting temperature is900℃,the roasting time is 90 min,the leaching temperature is 50℃,the leaching time is 60 min,the liquid-solid ratio is 12.5:1,the stirring speed is 400 rpm,and the lithium leaching rate is 79.52%.The content of Li,K,Na,and S in the secondary leaching residue is 0.062%,0.82%,2.13%,and 1.48%,respectively.（3）The optimal process parameters for ultrasonic enhanced leaching reaction are:leaching temperature 50℃,leaching time 60 min,leaching liquid-solid ratio 12.5:1,stirring speed 500 rpm,ultrasonic power 220W,and lithium leaching rate 82.47%.The content of Li,K,Na,and S in the secondary leaching residue is 0.060%,0.76%,2.15%,and 1.13%,respectively.（4）Research on leaching kinetics shows that the conventional leaching process is controlled by a mixed model,with an apparent activation energy of 20.17 KJ·mol^-1.The leaching process under ultrasonic conditions conforms to the interface control model,with an apparent activation energy of 16.27 KJ·mol^-1,indicating that ultrasonic can reduce the reaction activation energy.The SEM detection of the leaching residue shows that ultrasound can reduce the particle size of the leaching residue,making the surface of the particles smoother and smoother.This paper not only realizes the efficient recovery of lithium resources in the lithium leaching residue,but also effectively reduces the content of potassium,sodium and sulfur elements,laying a certain foundation for the large-scale use of building materials in the lithium leaching residue,which is of great significance to eliminate the environmental and ecological threats brought by the lithium leaching residue storage,and promote the healthy and sustainable development of lithium new energy.